1. Field of the Invention
This invention relates to a liquid-sealed vibration-proof device primarily used for supporting or bearing a vibration generator such as an automotive engine in an antivibratory manner.
2. Description of Related Art
Hitherto, as a liquid-sealed vibration-proof device for supporting an automotive engine or any other vibration generator so as not to transmit its vibrations to the vehicle body, there have been known a variety of ones versatile in structure.
For example, FIGS. 7 and 8 illustrate a liquid-sealed vibration-proof device of a two-chamber type constructed so that a cylindrical fitting (101) and an attachment fitting (103) are connected through a vibration-isolating base (102) made of rubber elastomer; a diaphragm (104) made of rubber membrane and a partition (105) located inwardly of the diaphragm (104) are fixed hermetically to an open end side of the cylindrical fitting (101) opposing the vibration-isolating base (102), thus partitioning an interior room between the vibration-isolating base (102) and the diaphragm (104) into two liquid chambers (107a)(107b) on the vibration-isolating base side and the diaphragm side; both liquid chambers (107a)(107b) are put in communication with each other through an orifice passage (106) formed in an outer periphery of the partition (105), whereby a vibration damping function and a vibration insulating function are achieved owing to the fluidization effect via the orifice passage and the antivibratory effect of the vibration-isolating base.
In the previous vibration-proof device, the partition (105) together with a reinforcement fitting (104a) the marginal portion of the diaphragm (104) are fitted from an open side of the cylindrical fitting (101) opposite to the vibration-isolating base (102) by press-fitting or inserting means and fixed by drawing of the cylindrical fitting (101) and crimping at its terminal edge so as not to be detached.
In assembling this vibration-proof device, in order that the aforementioned partition (105) to be press-fitted may be received and held in place within the cylindrical fitting (101), the vibration-isolating base (102) is formed at its inboard marginal part with a protuberant portion (120) having a step face (120a), with which an upper marginal portion (105a) of the partition (105) is in opposed contact, whereby permitting the axial positioning and supporting of the partition (105).
The aforesaid protuberant portion (120) as a positioning means has been heretofore formed so that the inside marginal part of the vibration-isolating base (102) is made thick-walled in its whole circumference so as to form the step face (120a) at the inboard side, as depicted in FIG. 8. Consequently, an effective rubber leg length (effective diameter) of the vibration-isolating base (102) performing a piston action attendant on the vibrations of the attachment fitting (103) becomes smaller by that.
Further, at the upper marginal portion (105a) of the partition (105) being in opposed contact with the step face (120a) there is formed a port opening (106a) of the orifice passage (106) at the outer periphery. However, since the positioning means due to the step face (120a) is formed in the whole circumference as mentioned above, it will shut partly or mostly the upside opening of the port opening (106a) even if the overhang is slight. Because of that, a sufficient flow through the orifice passage (106) cannot be ensured.
In order to ensure the flow through the orifice passage thereby achieving a sufficient vibration-damping characteristic, the port opening (106a) of the orifice passage (106) is required to ensure a predetermined opening area, but yet the step face (120a) shuts the port opening (106a) appreciably owing to the protuberant portion (120) for positioning, so that a sufficient vibration-damping characteristic cannot be exhibited.
To lengthen the circumferential width of the port opening with a view to solving the aforementioned problem will shorten the length of the orifice passage itself even if it is possible to ensure a sufficient opening area. Thus there are still problems of many restrictions in the aspect of characteristics and a poor practicability.
This invention has been made in view of the prior art problems, and accordingly, is aimed at furnishing a vibration-proof device, whose positioning means for the partition provided at the inner marginal part of the vibration-isolating base is comprised of protruding portions for positioning such that can perform its positioning function firmly, little shuts the port opening of the orifice passage in the partition, can secure sufficiently the opening area of the port opening even if it overlaps with the port opening, and can secure sufficiently the flow through the orifice without the necessity of making its circumferential width excessively large.
The present invention for solving the aforesaid problems is directed, in generic terms, to a liquid-filled vibration-proof device, wherein a cylindrical fitting and an attachment fitting are connected through a vibration-isolating base made of rubber elastomer; a diaphragm made of rubber membrane and a partition located inwardly of the diaphragm are fixed in a sealing manner to the opening side of the cylindrical fitting opposing the vibration-isolating base thereby to partition an interior room between the vibration-isolating base and the diaphragm into two liquid chambers; and both liquid chambers are put in communication with each other through an orifice passage defined in the partition. The liquid-sealed vibration-proof device is characterized in that the vibration-isolating base is provided at its marginal inner face with protruding portions for positioning so as not to obstruct the flow through a port opening of the orifice passage, the protruding portions being located circumferentially at a plurality of positions spaced apart at predetermined intervals.
According to this vibration-proof device, the plural protruding portions for positioning disposed on the inner face of the vibration-isolating base permit the partition to be fitted in the inner periphery of the cylindrical fitting to be positioned in place and besides, because of the fact that the plural positions for the protruding portions are circumferentially spaced apart at intervals, it is possible to keep the port opening open and to ensure sufficiently the flow through the orifice passage by deviating the position of the port opening of the orifice passage from the positions of the protruding portions.
In particular, by providing at least circumferentially the protruding portions for positioning to be spaced apart at intervals of a distance larger than the circumferential width of the port opening, the position of the port opening of the orifice passage in the partition can be located at the intermediate between two adjacent protruding portions for positioning, and accordingly, the port opening is by no means obstructed.
Moreover since the plural protruding portions are spaced apart at intervals as previously mentioned, an effective rubber leg length of the vibration-isolating base, namely an effective diameter thereof performing a piston action attended with vertical vibrations of the attachment fitting becomes larger by that, as a result of which the piston efficiency is elevated and the vibration damping performance can be enhanced.
In the previous vibration-proof device, it is preferred that the protruding portions for positioning be provided circumferentially at four or more positions spaced apart at intervals because the positioning function of the partition is thereby performed securely and the partition can be supported without causing any tilting, etc. For example, also in case where one of the protruding portions for positioning whose circumferential width is smaller than that of the port opening of the orifice passage overlaps with the port opening, the positioning of the partition is possible without causing tilting, etc.
The protruding portions for positioning are set such that they can perform the positioning function of the partition and retain a sufficient opening state of the port opening also where they overlap the port opening of the orifice passage. It is preferred that the circumferential width of the protruding portions be made smaller than the circumferential width of the port opening of the orifice passage. It is further preferred that in addition to this, a total length in circumferential width of all the protruding portions be xe2x85x9 to xc2xc the circumferential length of the orifice passage. Thereby the aforesaid positioning function can be performed firmly and even if one of them overlaps with the port opening, a required opening area can be ensured thereby to ensure a sufficient flow through the orifice passage.
Furthermore it is preferred that the protruding portions for positioning be formed so that in the condition that one of them overlaps with the port opening of the orifice passage, the opening area at the port opening excluding the overlapping part, on a plane, of the protruding portion may be larger than the area of the overlapping part. Owing to that, the port opening of the orifice passage is free from shutting in a manner to obstruct the flow while performing firmly the positioning function of the partition however the partition is incorporated in assembling.
The forms of working the invention will be hereinafter described with reference to examples as shown in the accompanying drawings.